Dolomite cation order in the geological record

Pina, Carlos M.; Pimentel, Carlos; García-Crespo, Ángel

doi:10.1016/j.chemgeo.2020.119667

Cited by 33 publications

(37 citation statements)

References 30 publications

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“…It has been argued that disordered dolomite, that is, mineralogically speaking, a very high-Mg calcite, can abiotically precipitate at ambient temperature from solutions containing polysaccharides, which is readily produced from degrading organic matter 49 . Recently, it was hypothesized that such disordered Ca-Mg carbonate precursors could serve as a reactive template to recrystallize to dolomite over time 10,14 . Thus, the involvement of microbes, whether direct or indirect, in the cold fracture system at Erzberg occupied by carbonate minerals that has been active since the last glaciation cannot be completely ruled out.…”

Section: Discussionmentioning

confidence: 99%

“…actors that control the origin and distribution of sedimentary dolomite in geologic records are intensely debated in the literature due to the much higher abundance of dolomites in ancient sedimentary rocks [1][2][3][4] , compared to modern marine and continental sediments 5,6 . This enigma is referred to as the "dolomite problem" [7][8][9][10] . Numerous mechanisms and models to explain the kinetic constraints on low-temperature dolomite formation in nature have been postulated, with the recognition of mineralogical, hydrogeochemical, and microbiological factors [11][12][13][14][15] .…”

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confidence: 99%

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Fracture dolomite as an archive of continental palaeo-environmental conditions

Baldermann

Mittermayr

Bernasconi

et al. 2020

Commun Earth Environ

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The origin of Quaternary dolomites in continental environments (e.g. karst and lakes) is barely constrained compared to marine dolomites in sedimentary records. Here we present a study of dolomite and aragonite formations infilling young fractures of the ‘Erzberg’ iron ore deposit, Austria, under continental-meteoric and low temperature conditions. Two dolomite generations formed shortly after the Last Glacial Maximum (~20 kyr BP): dolomite spheroids and matrix dolomite. Clumped isotope measurements and U/Th disequilibrium ages reveal formation temperatures of 0–3 °C (±6 °C) and 3–20 °C (±5 °C) for the both dolomite types, and depositional ages around 19.21 ± 0.10 kyr BP and 13.97 ± 0.08 kyr BP or younger, respectively. Meteoric solution and carbonate isotope compositions (δ18O, δ13C and 87Sr/86Sr) indicate the dolomites formed via aragonite and high-Mg calcite precursors from CO2-degassed, Mg-rich solutions. Our study introduces low temperature dolomite formations and their application as a sedimentary-chemical archive.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Fracture dolomite as an archive of continental palaeo-environmental conditions

Baldermann

Mittermayr

Bernasconi

et al. 2020

Commun Earth Environ

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“…The average degree of cation order calculated by the d015/d110 intensity ratio is 0.67 and ranges 0.36 -0.99 (1σ = 0.16) for (n=18) samples. The range of cationic ordering ratios represent poorly to well ordered dolomite, respectively (Kaczmarek and Sibley 2011;Pina et al, 2020). Most samples (n=13) are ≥0.60 which is indicative of relatively well ordered dolomite (Kaczmarek and Sibley 2011).…”

Section: Bulk Mineralogymentioning

confidence: 97%

Preservation of Organic Carbon in Dolomitized Cambrian Stromatolites and Implications for Microbial Biosignatures in Diagenetically Replaced Carbonate Rock

Murphy¹,

Wieman²,

Groß³

et al. 2020

Preprint

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Stromatolites have been a major focus in the search for ancient microbial biosignatures, in particular, stromatolites containing silicified microfossils. Silicification allows for the preservation of original textures and morphologies, which are important starting criteria in the characterization of fossils’ biogenicity and syngenicity to host rock. The microbial biosignatures of dolomitized stromatolites have not yet been characterized and correlated with their dolomitizing conditions. The Cambrian Allentown Formation in New Jersey is an excellent example of dolomitized stromatolites and thrombolites containing diagenetically modified microbial biosignatures. Based on XRD, ICP-OES, and EPMA data, the dolomite is ordered, and all three generations of dolomite are stoichiometric. The outcrop underwent early dolomitization by meteoric diagenesis and burial diagenesis resulting in multi-generational dolomite formation as follows: (1) The microspar dolomite formed by early replacement of precursory calcium carbonate minerals, at or very near the surface, where mixing of fresh and marine waters produced finely crystalline dolomite, (2) The zoned dolomite formed penecontemporaneously with the microspar phase as rhombohedral crystals by infilling primary pore spaces within the microspar matrix. Cloudy cores observed in many larger dolomite rhombs indicate recrystallization before the crystals grew outward in alternating stages, preserved in zoned rims, of Fe-enriched and -depleted fluids, (3) The saddle dolomite formed during late stage deeper burial with Fe- and Mn-rich fluids and occurs as void-filling, high-temperature phase. Organic carbon, characterized using confocal Raman microscopy, is exclusive to first generation microspar dolomite, and the D and G bands’ characteristics reveal similar style thermal alteration as host rock, indicating that the mapped organic carbon is syngenetic with the Cambrian stromatolites. This study offers a new way to investigate ancient life signatures preserved in secondary dolostones and may aid biosignature detection in ancient carbonate rocks on Mars.

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“…The stoichiometry and ordering of dolomite and calcite follow a ripening process through dissolution and reprecipitation of metastable or intermediate phases [30,31]. Additionally, other double carbonates, such as norsethite, were shown to form through dissolution-crystallization steps to evolve from metastable to stable mineral phases, with the solvent-mediated ripening process also promoting an increase in particle size [32].…”

Section: Magnesium Carbonate Formationmentioning

confidence: 99%

Effect of pH Cycling and Zinc Ions on Calcium and Magnesium Carbonate Formation in Saline Fluids at Low Temperature

Vandeginste

2021

Minerals

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The formation of dolomite is very challenging in the laboratory under ambient conditions due to kinetic inhibition. The goal of this study was to test the impact of pH cycling and zinc ions on the formation of magnesium-rich carbonates in saline fluids at a low temperature. Batch reactor experiments were conducted in two series of pH cycling experiments, one without and one with zinc ions, at 43 °C. The results after 36 diel pH cycles indicate a reaction product assemblage of hydromagnesite, aragonite and magnesite in the experiments without zinc ions, and of magnesite and minor aragonite in the experiments with zinc ions. The presence of zinc ions leads to a decrease in the pH in the acid phase of the cycling experiments, which likely plays a role in the reaction product assemblage. Moreover, the hydration enthalpy and other specific ion effects could be additional factors in the formation of magnesium-rich carbonate. The results show a clear evolution towards increasing incorporation of magnesium in the carbonate phase with cycle number, especially in the experiments with zinc ions, reflecting a ripening process that is enhanced by pH cycling. Hence, repeated pH cycling did not lead to more ordered dolomite (from protodolomite), but rather to the formation of magnesite with 92 mol% MgCO3 after 36 cycles, even though geochemical models indicate a higher saturation index for dolomite than for magnesite.

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Dolomite cation order in the geological record

Cited by 33 publications

References 30 publications

Fracture dolomite as an archive of continental palaeo-environmental conditions

Fracture dolomite as an archive of continental palaeo-environmental conditions

Preservation of Organic Carbon in Dolomitized Cambrian Stromatolites and Implications for Microbial Biosignatures in Diagenetically Replaced Carbonate Rock

Effect of pH Cycling and Zinc Ions on Calcium and Magnesium Carbonate Formation in Saline Fluids at Low Temperature

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